It may not be a mobile version of Adobe Illustrator, but Skitch can handle basic image annotations and sketches exceptionally well. It's easy to learn, its tools work well, and it can even export your work to Evernote.
Getting started with Skitch is simple. From the Home screen, you can open up a blank canvas, import an image from your gallery, or take a new photo with your mobile device's camera. Also new to Skitch is a feature that lets you pull up and add annotations directly onto a Google Map, which is perfect for giving detailed or otherwise complicated directions to friends. It's also a nice tool for creative uses like scavenger hunts.
The editor interface is clean, with tons of white space in order to accommodate as large a canvas as possible. Two thin tool bars run up either side of the screen, with neither being overwhelming in any way. The right-hand bar offers basic functions like Home, Crop, Trash, Undo/Redo, Save, and Export to Evernote, while the left-hand bar houses all of your basic drawing tools like Pen, Arrow, Selection, Text, and Shape. There's also a selector on the left that lets you choose the color and width of your strokes.
Hands down, the best thing about Skitch is its simplicity. True, it's not quite a designer's dream come true, but it sure is easy to whip out and scrawl away on. The Pen tool works nicely, and even smooths out your lines as you draw them. I love the Selection tool because it makes it easy to move, edit, or delete strokes, and it lets you select multiple elements if you use it like a lasso. And of course, you can add rectangles, lines, ovals, or even arrows to your document in just a couple of taps.
Finally, since Skitch is owned by the developers of Evernote, it comes pretty tightly integrated with the popular note-taking app. In one tap, you can save your work directly to a Notebook on your account, which is perfect for someone who might be tracking sources of visual inspiration.
Overall, Skitch is an incredibly simple drawing and annotation app that's perfect for those with creative inclinations. I highly recommend downloading it, especially if you're an avid Evernote user.